#include<iostream>
#include<cmath>
using namespace std;
int main()
{
	int n,a[1001],maxx=0,b[1001];
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	for(int i=1;i<=n;i++)
	{
		if(int(sqrt(a[i]))*int(sqrt(a[i])) != a[i])
		{
			b[i]=a[i];
		 } 
	}
	for(int i=1;i<=n;i++)
	{
		if(b[i]>maxx)
		{
			maxx=b[i];
		}
	}
	cout<<maxx;
	return 0;
}